Xie Changji, Zheng Zhanguang, Li Li, Sun Teng
College of Mechanical Engineering, Guangxi University, No. 100 Daxue Dong Road, Nanning 530004, China.
Key Laboratory of Disaster Prevention and Structural Safety of Ministry of Education, Guangxi Key Laboratory of Disaster Prevention and Engineering Safety, Guangxi University, No. 100 Daxue Dong Road, Nanning 530004, China.
Materials (Basel). 2024 Aug 17;17(16):4088. doi: 10.3390/ma17164088.
In the serviced components of a 7075 aluminum alloy, the propagation of fatigue crack can be retarded because of the overload effect; however, the corresponding retardation mechanisms are complex. To provide further insights into the retardation mechanisms of 7075 aluminum alloys, this study addresses the crack tip damage response of a cracked 7075 aluminum alloy under an overload effect. Based on the dual-scale modeling approach and the damage-coupled crystal plasticity model, the effect of the microstructure of a 7075 aluminum alloy on the damage behavior ahead of the crack tip under an overload was studied. The factors affecting fatigue damage accumulation ahead of the crack tip, such as dislocation density, the variation in the activities of slip systems, and the orientation effect of the nearest neighbor grains, are described. The results show that for the 7075 aluminum alloy, the compressive residual stress induced by the overload effect not only decreases the number of activated slip systems, but also lowers the rate of increase in dislocation density. This causes a decrease in fatigue damage accumulation during deformation. Moreover, the overload effect decreases the slip system activity as well as the resultant plastic slip; however, the decrease in plastic slip varies with the grain orientation, indicating that the overload effect depends on the grain orientation. It can also be found that both the damage strain energy release rate and lattice strain are influenced by the orientation of the nearest neighbor grains, which can eventually affect the overload effect. These findings contribute to understanding the retardation mechanisms from a microscopic perspective and provide guidance on improving the material design of a 7075 aluminum alloy to some extent.
在7075铝合金的服役部件中，由于过载效应，疲劳裂纹的扩展可以得到延缓；然而，相应的延缓机制较为复杂。为了进一步深入了解7075铝合金的延缓机制，本研究探讨了裂纹7075铝合金在过载效应下裂纹尖端的损伤响应。基于双尺度建模方法和损伤耦合晶体塑性模型，研究了7075铝合金微观组织对过载下裂纹尖端前方损伤行为的影响。描述了影响裂纹尖端前方疲劳损伤累积的因素，如位错密度、滑移系活动度的变化以及最近邻晶粒的取向效应。结果表明，对于7075铝合金，过载效应引起的压缩残余应力不仅减少了激活的滑移系数量，还降低了位错密度的增加速率。这导致变形过程中疲劳损伤累积减少。此外，过载效应降低了滑移系活动度以及由此产生的塑性滑移；然而，塑性滑移的降低随晶粒取向而变化，表明过载效应取决于晶粒取向。还可以发现，损伤应变能释放率和晶格应变都受最近邻晶粒取向的影响，这最终会影响过载效应。这些发现有助于从微观角度理解延缓机制，并在一定程度上为改进7075铝合金的材料设计提供指导。
